1. Field of the Invention
This invention relates to a semiconductor sensor consisting of a silicon wafer and a glass substrate and a method for manufacturing the same, whereby, when a silicon wafer having a diaphragm is bonded with a glass substrate through anodic bonding process, the glass substrate contains a dielectric material and a recess or a cavity so as to prevent a bond from occurring between the glass substrate and the silicon wafer.
2. Related Art
In FIG. 6, anodic-bonding process proceeds with the following steps. A silicon wafer 201 having a smooth surface 201a and a diaphragm 201b is bonded to a glass substrate 202 (for example, pyrex glass). After that, a unit containing the silicon wafer 201 and the glass substrate 202 is heated in the range of 300.degree. C. -400.degree. C. by a hot plate 204. Under this condition, when a negative voltage within 500-1000 V is applied to the glass substrate 202 by a negative electrode 203, a large electrostatic attracting force is generated between the silicon wafer 201 and the glass substrate 202 so that the chemical bonding occurs between the silicon wafer 201 and the glass substrate 202 at a boundary surface. However, in this voltage applying step, the diaphragm 201b serving as an undesired bonding portion at the time of performing the anodic bonding process is bonded to the glass substrate 202, because the large electrostatic attracting force is generated between the silicon wafer 201 and the glass substrate 202.
In view of this problem, for example, in Unexamined Japanese Utility Model Application No. sho. 3-88137, an oxide layer is formed on both sides of the diaphragm so as to prevent a bond from occurring between the diaphragm 201b and the glass substrate 202. However, if this structure is employed, it is difficult to ensure the sufficient sensitive characteristic.